1. Industrial Field of the Invention
The present invention relates to an epoxy resin composition for an interlayer insulating material in a multilayer printed-wiring board of the build-up type which is formed by stacking alternately conductor circuitry layers and insulating layers, the cured product of the composition exhibiting both high thermal resistance and capability of being roughened with an oxidizing agent. It also relates to an adhesive film and a prepreg made by using the composition, a laminate and a multilayer printed-wiring board made by using them, and a process for manufacturing the same.
2. Prior Art
As a process for manufacturing a multilayer printed-wiring board, attention has recently been focused on the build-up type technique wherein an organic insulating layer is formed alternately on a conductor layer of an internal-layer circuit board. Japanese Patent Application Laid-Open (Kokai) Nos. 304931/1995 and 304933/1995 disclose a process for manufacturing a multilayer printed-wiring board which process comprises the steps of coating an internal-layer circuit board having a circuit formed thereon with an epoxy resin composition, curing it under heating, forming an unevenly roughened surface thereon with a roughening agent and forming a conductor layer by plating. And, Japanese Patent Application Laid-Open (Kokai) No. 64960/1996 also discloses a process for manufacturing a multilayer printed-wiring board which process comprises the steps of applying an undercoat adhesive, drying it preliminarily, bonding an additive adhesive in the film form thereto, curing it under heating, roughening it with an alkaline oxidizing agent and forming a conductor layer by plating. As a curing agent for the epoxy resin composition used for these purposes, an amine-type curing agent such as dicyandiamide, an imidazole compound or the like has been generally used. With the recent increase of real loading density, however, similarly to the laminate type, a curing system exhibiting stronger thermal resistance as compared with a conventional system is desired for an interlayer insulating material of the build-up type. As a method for solving such a problem, the inventors have developed an epoxy resin composition for an interlayer insulating material exhibiting both high thermal resistance and capability of being roughened with an oxidizing agent using a phenolic curing agent containing a triazine structure as shown in Japanese Patent Application Laid-Open (Kokai) No. 1547/1999. However, the resin composition of the present invention essentially necessitates a roughening component such as rubber component, the thermal resistance or electric insulation has sometimes come into question in the fields where a finer pattern or a thinner insulating layer is required. Furthermore, in the case where an epoxy resin containing a phosphorus atom which attracts attention as a flame retardant epoxy resin, is used instead of a bromine-type epoxy resin from the viewpoint of recent environmental problems, there exists the problem that a conventional resin composition does not afford any well-roughened surface and therefore, peeling strength of the resulting plated conductor layer is poor.
Problems to be Solved by the Invention
Therefore, it is an object of the present invention to develop an epoxy resin composition for an interlayer insulating material exhibiting both high thermal resistance and capability of being roughened with an oxidizing agent, more particularly, an epoxy resin composition which is capable of giving a finer pattern and making an insulating layer thinner, the cured product of which exhibits good thermal resistance and electric insulating property, and improves peeling strength of the resulting plated conductor layer.
Other objects and advantages of the present invention will be apparent from the following description, drawings, and disclosure.
In view of the aforementioned problems, the present inventors have studied intensively and succeeded in developing an epoxy resin composition for an interlayer insulating material capable of being roughened with an oxidizing agent without necessitating a roughening component in a system of using a phenolic curing agent, on the basis of which the present invention has been made.
Namely, a first embodiment of the present invention relates to an epoxy resin composition comprising, as the essential components, (A) an epoxy resin having two or more epoxy groups in one molecule, (B) a phenolic curing agent, (C) a phenoxy resin containing a bisphenol S skeleton and having a weight average molecular weight of 5,000 to 100,000, and (D) a curing accelerator.
Particularly, preferred is the epoxy resin composition wherein the epoxy resin (A) contains a phosphorus atom, the phenolic curing agent (B) contains a nitrogen atom, and the phenoxy resin (C) contains a bisphenol S skeleton and a biphenyl skeleton.
A second embodiment of the present invention relates to an adhesive film which is obtainable by forming a thin film of the epoxy resin composition of the present invention on a supporting base film.
A third embodiment of the present invention relates to a prepreg which is obtainable by coating and/or impregnating a sheet-shape reinforced base material made of a fiber with the above-described epoxy resin composition.
A fourth embodiment of the present invention relates to a multilayer printed-wiring board wherein a plated conductor layer is formed on the roughened surface of a cured product of the above-described epoxy resin composition and the other surface is closely laminated onto a patterned internal-layer circuit board.
A fifth embodiment of the present invention relates to a multilayer printed-wiring board which is obtainable by the steps of coating a patterned internal-layer circuit board with the above-described epoxy resin composition, curing it under heating, roughening the surface of the cured product with an oxidizing agent, and forming a conductor layer on the roughened surface by plating;
a multilayer printed-wiring board which is obtainable by the steps of laminating the above-described adhesive film on a patterned internal-layer circuit board under conditions of pressurizing and heating, detaching the supporting base film, if necessary, curing the epoxy resin composition under heating, roughening the surface of the cured composition layer with an oxidizing agent, and forming a conductor layer on the roughened surface by plating; and
a multilayer printed-wiring board which is obtainable by the steps of laminating the above-described prepreg on a patterned internal-layer circuit board under conditions of pressurizing and heating to integrate them, roughening the surface of the prepreg with an oxidizing agent, and forming a conductor layer on the roughened surface by plating.
A sixth embodiment of the present invention relates to a process for manufacturing a multilayer printed-wiring board comprising the steps of coating a patterned internal-layer circuit board with the above-described epoxy resin composition, curing it under heating, roughening the surface of the cured composition with an oxidizing agent, and forming a conductor layer on the roughened surface by plating;
a process for manufacturing a multilayer printed-wiring board comprising the steps of laminating the above-described adhesive film on a patterned internal-layer circuit board under conditions of pressurizing and heating, detaching the supporting base film, if necessary, curing the epoxy resin composition under heating, roughening the surface of the cured product layer with an oxidizing agent, and forming a conductor layer on the roughened surface by plating; and
a process for manufacturing a multilayer printed-wiring board comprising the steps of laminating the above-described prepreg on a patterned internal-layer circuit board under conditions of pressurizing and heating to integrate them, roughening a surface of the prepreg with an oxidizing agent, and forming a conductor layer on the roughened surface by plating.
A seventh embodiment of the present invention relates to a laminate which is obtainable by the steps of coating a surface formed by etching out a copper foil of a copper foil-clad laminate on both sides or at least one surface of an unclad laminate with the above-described epoxy resin composition, and curing it under heating;
a laminate which is obtainable by the steps of laminating the above-described adhesive film on a surface formed by etching out a copper foil of a copper foil-clad laminate on both sides or at least one surface of an unclad laminate under conditions of pressurizing and heating, detaching the supporting base film, if necessary, and curing it under heating;
a laminate which is obtainable by laminating the above-described prepreg on a surface formed by etching out a copper foil of a copper foil-clad laminate on both sides or at least one surface of an unclad plate under conditions of pressurizing and heating; and
a laminate which is obtainable by laminating the above-described prepreg under conditions of pressurizing and heating.